Buxbaumia Hedwig, 1801.

Buxbaumia aphylla growing on rotten wood, photo by Wilson

The capsule shape make identification to genus certain.

Key to Buxbaumia

In this key we treat one of the most distinctive of mosses. The gametophytes, male or female, are essentially invisible to the naked eye; but the sporophytes are larger than those of most other mosses. The seta is distinctive in the high papillosity that cloaks its entire length, and this seta may be the only item visible during much of the year because of the intensity of mouse predation on the capsules. The capsules are asymmetric in a manner that suggests that an originally fat and cylindrical capsule has been pressed between the fingers in the shape of an oil lantern.

Species included in this key are in Buxbaumiaceae:
Buxbaumia aphylla Hedwig
Buxbaumia piperi Best
Buxbaumia viridis (A. P. de Candolle) Mougeot & Nestler

Two species of Buxbaumia have green capsules and grow on rotten logs. Buxbaumia piperi is the more common of these two species, and it primarily appears in early spring. The other log species, Buxbaumia viridis, is rarely encountered in late summer and autumn. Buxbaumia aphylla has brown capsules that arise from pressed mats of organic soil, especially that occupied by the lichen genus Cladonia (reindeer moss).

A. Cuticle of capsule rolling back from mouth when that capsule is deoperculate and fully dry .....B
A. Cuticle separating along a dorsal split and peeling back laterally .....Buxbaumia viridis

B. Capsule glossy reddish-brown when dry and recently deoperculate; plant mostly on organic soil (in this area) .....Buxbaumia aphylla
B. Capsule green to pale yellowish-brown, not at all glossy; plant mostly on logs, common .....Buxbaumia piperi